Rheostat



Patented July 3, 192153o UNri so sraries PATENT QFFICE.

ERNEST G. DANIELSON, F SAN FRANCSCD, CLIFGItNA, ASSIGNOR TO E. T. CUM; NINGHAB, OF SN FRANCSCC", CALIFORNEA.

RHESTAT.

Application tiled July 18, 1921. Serial No. 485,698.

T 0 all whom t may cof/worn.'

Be it known that l. ERNEST G. lil-livraison., a-c'itizen of the United States.y and a resident of the citv and county of San Francisco State of California` have invented certain new and useful Rh'eostat, of which the tollowing is a specification.

The invention relates to small rliebosta'ts vlor varying the resistance of an electric circuit, and particularly to panel typerneostats. I

An object oic the invention is to provide an inexpensive rheostat ol simple construction.

Another object oi' the invention is to provid@ a mounting for a helical resistance nient` so that air is lree to circulate through the element to keep it cool.

The invention possesses lother advantageous features, some of which the foregoing. will be set forth at length in the to'llovvlingr description Where l shall outline in lull, that forni of the invention which l have selected for illustration in 'the drawings accompanying and forming part or the present specification.

In said drawings:

Fig. l is a rear view of the rlieosiat mounted on a panel. j

Fig. 2 is a side elevation oi, the rheostat.

Fig. 3 is a vertical section through the resistance element mounting. K

The rheostat of my invention comprises a moulded disc 2 of bakelite or other similar dielectric which is adapted to be secured by screws to a panel 3. The disc is provided -with a peripheral flange curved in cross section and springing' forward from theu face of the disc, to forni a llow peripheral groove, in which the helically coiled resist-- ance element 5 in disposed. and in which it is preferably adhesively secured. The resistance element projects radially beyond the edge of the disc, so that the greater portion of 'the wire ot the resistance element is exposed over its Whole surface lto the air, there by providing 'for maximum air cooling of the resistance element.

At one portion of its periphery the disc is provided 'with a boss- 6, which is disposed between the ends of the resistance element.

@ne end of the resistance element is con* nected to a binding post 7 and the other end isancliored in the disc or in the boss. One Wire of the circuit, the resistance of which is to be varied. is connected to the binding post 7 and the other Wire is connected to the binding; post 8, the binding posts consist-ing oi screws seated in the boss.

Extending through the panel and the disc is a. rod 9. having on its forward end a knob l2 and a pointer `l? which is movable over a scale on the face of the panel. Secured to the rear end ot' the iod is a resilient Contact arzii 14, which is electrically connected to the bindingpost 8 by a resilient metallic strip l5` held in place by the binding post B and having an aperture in its other end through which the rod passes, the resiliency in the strip keeping it in pressure contact with the contact arm holding nut 16. The outer end ol the contact arm is bent so that the. contact end l? lies substantially tangential to the helix of the resistance element, thus providing a smooth iiat surface contact. 'Rotation ot the knob nioves the Contact arm over the helix to vary the amount of resistance in the circuit.

lf claim:

l. ln a rheostat, a circular disc having a peripheral groove, a conductor coiledzn the torni of a long' helix held within the groove, said groove being' so shallow that the major portion of the helix is exposed, and a I'iat resilient contact arm of a single piece of metal rotatable on an axis passing through the center of the disc, said arm having a sur face contactingr with thehelix on a plane oblique to the anis. I

In a rlieostat, a. resistance element, a Contact arm rotatable to vary the point of connection between it and the resistance element, a rod, means 'for supportingr the rod,

said rod passing through the contact arm,

means for fastening the arm to the rod whereby the rod may serve to rotate the arm, and means for making an electrical con? nection to the coi'itact arm comprising a fiat metallic spring 'fastened at one end to the rod support and havinfgr its free end bearing against the arm fastening means.

In a rheostat, a thin circular disc of insulation material, said disc having a, narrow curved flange extending from one of its thereof to provide zjgrcumferential groove? a conductor coiled` in the form ofe long helix having a, diameter substantially l@ rger than the width of the groove and held within the groove, and a rotatable Contact arm for making an electrical connection to the helix.

In testimony whereof, I have hereunto set my hand.

ERNEST Gf. DANIELSON. 

